This study investigated how a child's level and pattern of performance affected teachers' perception of the cause of the hild's performance and teacher's evaluation of the child and his characteristics. Pairs of either teachers, student teachers, or education students participated in the study, accepting the role of participant or observer. The participants taught a fifth grade student a mathematics lesson for three 5-minute trials, while the observer watched the participant during her task. Data from 108 subjects were subjected to analysis of variance. The results provided some support for the presence of ego-relevant attributional biases in teachers. In some instances participants appeared to show ego-defensive biases, while in other cases, participant responses were identical to those of observers. Participants sometimes appeared to be trying hard to be non-biased and to avoid ego-protecting or enhancing attributions. This study observes the interaction of the participant and observer, to find who influences whom. Further research is needed to assess the influence of other persons upon teachers. Included in this study is a ten-item bibliography and appendixes with testing instructions, post-experimental and post-trial questionnaires, and lessons. (MJM)